Why does performance increase as resolution is increased?

[Jetrise]

Hi All,

 

Quick question for the community, my friend was getting horrific FPS in games such as Squad and Warzone. While watching task manager, we noticed the CPU was a bottleneck. After a bit of trial and error, we switched from a 1080p monitor to a 1440p monitor and noticed his FPS almost double in these titles, and CPU usage was not constantly at 100%. Could someone explain to me how CPU performance decreases when you increase the resolution of the monitor? I've done a bit of googling around this topic and I can't seem to understand it.

 

Specs for reference:

CPU: i5 4690K

GPU: GTX 1650 Super

RAM: 16GB

[GER_T4IGA]

That's not how it works. As I understood it, the CPU sets a rough limit for the FPS you can reach at a given set of settings (excluding the resolution). When you increase the render resolution you shouldn't be able to achieve a higher FPS, no matter what. I'd expect your testing methodology to be flawed, sry.

[SupaKomputa]

That doesn't make sense, if you game at 1440p, the FPS should drop especially if you have 1650 super.

 

As for the cpu load decrease, that is normal, when you have lower fps (for the higher resolution), the load will be more on the gpu.

[Downkey]

14 minutes ago, Jetrise said:

Hi All,

 

Quick question for the community, my friend was getting horrific FPS in games such as Squad and Warzone. While watching task manager, we noticed the CPU was a bottleneck. After a bit of trial and error, we switched from a 1080p monitor to a 1440p monitor and noticed his FPS almost double in these titles, and CPU usage was not constantly at 100%. Could someone explain to me how CPU performance decreases when you increase the resolution of the monitor? I've done a bit of googling around this topic and I can't seem to understand it.

 

Specs for reference:

CPU: i5 4690K

GPU: GTX 1650 Super

RAM: 16GB

This may sound stupid. but are you sure you weren't originally using a 4k monitor?

[Mark Kaine]

Why buy new gpu when you can just up the resolution!

 

Genius!  

 

 

Except that's not how it works lol sorry. 

 

 

[Jetrise]

This is what I thought also. I checked that he was accidently rendering at a higher resolution when displaying 1080p.

 

Nope, was most certainly on a 1080p going to 1440p @Downkey.

 

I came across this article when googling which may explain it: https://www.reddit.com/r/buildapc/comments/9ikrwz/why_does_increasing_resolution_lower_cpu_load/

[Aereldor]

That's GPU bottlenecking. 

 

Think of PC performance as horses pulling a carriage. At 1080p, the GPU isn't too stressed, so the GPU 'horse' can run at full speed. Since the GPU horse is running at full speed, the CPU horse can also run at full speed.

 

At 1440p, that's almost twice as many pixels as 1080p. The carriage is twice as heavy, and the GPU horse can't go as fast anymore. As a result, no matter how strong the CPU horse is, it can only run at the speed set by the GPU horse. 

This can work vice versa.

[Mark Kaine]

14 minutes ago, Jetrise said:

This is what I thought also. I checked that he was accidently rendering at a higher resolution when displaying 1080p.

 

Nope, was most certainly on a 1080p going to 1440p @Downkey.

 

I came across this article when googling which may explain it: https://www.reddit.com/r/buildapc/comments/9ikrwz/why_does_increasing_resolution_lower_cpu_load/

 

from your link :

 

Quote

The resolution in and of itself doesn't have anything to do with it. Your CPU gets taxed when the framerates are high. Gaming at a higher resolution puts more work on the video card - making it harder to generate higher framerates. Lower framerates means less work for the CPU.

 

 

12 minutes ago, Aereldor said:

That's GPU bottlenecking. 

 

Think of PC performance as horses pulling a carriage. At 1080p, the GPU isn't too stressed, so the GPU 'horse' can run at full speed. Since the GPU horse is running at full speed, the CPU horse can also run at full speed.

 

At 1440p, that's almost twice as many pixels as 1080p. The carriage is twice as heavy, and the GPU horse can't go as fast anymore. As a result, no matter how strong the CPU horse is, it can only run at the speed set by the GPU horse. 

This can work vice versa.

Thats a good explanation and it can actually go both ways, yes. But what I don't know is how rare is this actually, it seems it would only work with games that have a heavy imbalance in some way?

 

 

Edit: like for example if I play MHW with my new and shiny RTX 3070 at 1080p it'll be like... 50% gpu usage, 25% cpu usage, on average. 

 

But if I up the resolution to 1440p (with NVIDIA DSR) I'll get close to 100% gpu usage, and cpu usage will stay roughly the same although it may even go down slightly, like 15-20%... (I'd need to check this more thoroughly though) 

 

So yeah, in other words how bad has the bottleneck actually to be for this to occur (higher fps at higher res, it seems nearly impossible)? 

[Jetrise]

I am as confused as everyone else is. It makes zero sense to me, thus my question. But, he is now playing games with 60% (1440p) CPU usage instead of 100% (1080p). GPU usage has also increase. Before, he was around 70% of 3D usage, now it is constantly maxed out. In Squad, he was getting an average FPS of 31, now he is getting 60. It makes absoluetly zero sense to me, that's why I am here. 

[Mark Kaine]

13 minutes ago, Jetrise said:

I am as confused as everyone else is. It makes zero sense to me, thus my question. But, he is now playing games with 60% (1440p) CPU usage instead of 100% (1080p). GPU usgae has also increase. Before, he was around 70% of 3D usage, now it is constantly maxed out. In Squad, he was getting an average FPS of 31, now he is getting 60. It makes absoluetly zero sense to me, that's why I am here. 

Basically I think I figured it out... in practice this *only* works if you're 100% CPU bound, then upping the resolution can actually take away stress from the cpu because the gpu has to do more work now. 

 

I believe this would also have something to do with the game engine, and of course the actual imbalance of the pc build overall. 

 

Like I've described above, this sort of effect would be impossible with all hardware combinations I had so far with MHW, because I *know* for sure the game will instantly drop frames when gpu hits 100%...

 

 

of course this would also happen if cpu hits 100%, but this just seems extremely unlikely with a modern multi threaded cpu as the engine is heavily optimized for multi threading (MT Framework 3.0*)

 

*MT" stands for "Multi-Thread", "Meta Tools" and "Multi-Target". While initially MT Framework was intended to power 2006's Dead Rising and Lost Planet: Extreme Condition only, Capcom later decided for their internal development divisions to adopt it as their default engine.

 

 

 

 

[Jetrise]

Thanks for the feedback all. I'm still not 100% sound why this works, but, I will remember it in the future. 

[Aereldor]

1 hour ago, Mark Kaine said:

what I don't know is how rare is this

Uh, it's not rare. Literally every single game has a bottleneck... Whether that's the CPU, GPU, RAM, or even the engine itself.